Years ago, I visited the Grand Canyon with my family. The beauty of it was overwhelming, and everything they say about it is true. It’s magnificent.

That grandeur is only amplified by the obvious scientific significance of it. The layers of sedimentary rock, exposed by the eons-long patient erosion of the Colorado river, are a dramatic open textbook of the geological history of our planet, as if the Earth itself is saying "Look here, and learn of the past!"

What you’re seeing here is a topographical model of a small part of a crater floor on Mars: Gale Crater, to be precise, a monster 150 km (90 miles) wide impact located nearly on the equator of Mars. In its center rises a mountain, a central peak common in large impact craters. Surrounding this central peak is an enormous mound of material, rising kilometers above the crater’s floor (see the topographic image below; the ellipse represents an old potential landing site of the Spirit rover). It’s not entirely clear how this mound formed; however, it’s likely that the entire crater was once filled with material laid down as periodic deposits, and that most of it has eroded away, leaving just that lopsided mound.

If that sounds familiar, it may be because the Grand Canyon has a similar history (without the crater, of course).

And like its terrestrial counterpart, the exposed layers tell a history of Mars’s geologic past. Scientists studying those layers using images from the HiRISE camera on the Mars Reconnaissance Orbiter have uncovered a startling feature: while sulfates (deposited by salty water) are seen throughout the layers, clays are only seen lower down, deeper into the past. Clays are only seen where water is abundant, but sulfates alone indicate conditions where water evaporated away.

What the floor of Gale Crater appears to be telling us is that standing water, at least locally, existed long ago on Mars, but later evaporated away. This is consistent with what we have seen in other parts of Mars, of course. Ever since the rovers landed on Mars we’ve seen one piece of evidence after another of standing water in the Red Planet’s distant past.

But there’s something about this news that appeals to me, that touches more than the scientist part of my brain. If I hadn’t told you that first image was from Mars, you might very well think that it was from the Grand Canyon or some other Earthly feature. And it really is a canyon, as you can see from this HiRISE image of the same area:

This image shows the very lower left of the oblique view shown above. It’s upside-down, making features difficult to compare (check out the full HiRISE image of the area to see the whole thing), but the crater floor is at the top of this false-color image, and the mound begins to rise toward the bottom. You can see the canyon carved right into the floor, with sand dunes rippling across it.

Whatever carved this canyon, perhaps hundreds of millions of years ago, perhaps more, tore away the deposited material and revealed all those layers of rock. These layers can be read like a history book written in reverse chronological order, showing us the deep past of Mars, and telling the sad tale of how an entire planet lost its water.

Mars was once more like the Earth is now, though just how much is anyone’s guess at the moment. I doubt it was exactly like Earth; the evidence of water we see indicates it was incredibly salty, far saltier than we have here at home. But still, Mars is a brilliant ochre cautionary tale in our sky. There but for the grace of water go we…

But does this yield any information on whether or not the water does in fact contain sentient viruses intent on piggybacking to Earth? These are questions that must be answered before we risk a manned mission!

<creationist mode>
Just as you’d think creationists were losing support by scientists about the biblical flood theory of the Grand Canyon formation.

Here is what Phil Plait had to say about the creationists supporting global flood geology:
“Years ago, I visited the Grand Canyon with my family. The beauty of it was overwhelming, and everything they say about it is true.” -Phil Plait
</creationist mode>

(I consider that my attempt at quote mining deserves bonus points, since the paragraph directly after what I quoted completely contradicts it and proves that I am full of it. But I am not full of it, I am merely persecuted. And you all know how I like being persecuted *wink* *wink* *nudge* *nudge*.)

I think it’s totally wasteful of resources to mount manned expeditions to the Grand Canyon. I think we should focus our limited budget on scientific robotic expeditions, and just look at the pretty pictures that produces. If private industry wants to visit it in person, fine.

I doubt it was exactly like Earth; the evidence of water we see indicates it was incredibly salty, far saltier than we have here at home.

Well, we do have some incredibly salty waters on Earth too – the Dead Sea in Israel and, when they have water in them, South Australia’s Lake Eyre, the USA’s Bonneville (spelling?) salt flats, Utah’s Great Salt lake, Lake Mono (I think) and so on. How do they compare with the saltiness of Mars?

Actually, even in the south east corner of my home state of South Australia there’s a small lake of highly salty water called the Pool of Siloam which I’ve personally swum in myself!

Water on the Bonneville salt flats is seasonal; they are usually bone dry in August. Beautiful place to visit (seen a few drag races and a few model rocket launches there), but do not forget your sunblock.
It could be argued the Great Salt Lake is the non-seasonal part of the Bonneville Salt Flats.

I’d suggest it would be more accurate to state that an “entire planet lost its’ water” w/o referring to the “how”. I saw little in your post that would posit the “how” of water loss. THAT might take another, longer post.(granted, you were probably referring to the historical “how” rather than the mechanism of water loss, but still,,,)

Now, if we could just figure out how to move Venus to the orbit of MArs,,,

Water on the Bonneville salt flats is seasonal; they are usually bone dry in August. Beautiful place to visit (seen a few drag races and a few model rocket launches there), but do not forget your sunblock. It could be argued the Great Salt Lake is the non-seasonal part of the Bonneville Salt Flats.

Okay thanks – I didn’t know that last bit there.

I *did* know about the seasonal or often dry nature of Bonneville Salt Flats though – that’s why I prefaced it and Australia’s Lake Eyre with ” … and, when they have water in them…” in my comment originally. (#12)

Anyone know how the saltiest waters on Earth compare with the salty waters of Mars? Equally salty? Saltier? Less salty?

@M_T_U Don Juan Pond is about as salty as it gets. It’s so salty that it doesn’t freeze in winter even when the temp reaches -30C. It’s less than a foot deep. Still supports life. Lake Vanda nearby, is about 2/3 as salty and more lake-like in depth and extent. Outside Antarctica’s dry valleys, there’s a crater lake in Africa and then the Dead Sea.

More interesting then the question of how the water on Mars was evaporated away is the realization that there was a point when water flowed as a liquid on the surface next to a geological record which allow correlation with historic climate periods on Earth.

In the previous thread Phil Says:
February 21st, 2010 at 12:03 pm
Jason (55): The Sun is not the cause of global warming on other planets. If Mars were warming a little, the Earth would warm a LOT. Read this.

Mars lost its water when the “Fifth Planet” exploded
to create the asteroids. This is evidenced by
the one side of Mars which is heavily cratered.
Any intelligent astrophysicist could figure this out.
den
*****